disposal of excreta
TRANSCRIPT
DISPOSAL OF EXCRETA
Health hazards of improper excreta disposal
• Soil pollution• Water pollution• Contamination of foods• Propagation of flies
Spread of disease from excreta
Sanitation barrier
Methods of excreta disposal
Unsewered areas
• Service type latrines( conservancy system)
• Non service type( sanitary latrines)
• Latrines suitable for camps and temporary use.
Non service type( sanitary latrines)
• Bore hole latrine
• Dug well latrine
• Water seal latrine
PRAI type
RCA type
Sulab shauchalaya
• Septic tank
• Aqua privy
Latrines suitable for camps and temporary use.
Shallow trench latrine Deep trench latrine
Pit latrine Bore hole latrine
Primary treatme
nt
•Screening •Removal of grit•Plain sedmentation
Secondary
treatment
•Trickling of filters•Activated sludge process
Other method
s
•Sea out fall•River outfall•Sewage farming•Oxidation ponds
Sewered areas
Cartage (Conservancy system)•Example: Bucket latrine
•Disadvantages:
oSmell
oFlies
oHealth risk to people handling the
excreta
oHealth risk from food crops
fertilized with raw excretaBucket latrine
Criteria for a sanitary latrine
• Excreta should not contaminate the ground and surface
water.
• Excreta should not pollute the soil.
• Excreta should not be accessible to flies, rodents,
animals
• Excreta should not create a nuisance due to odor or
unsightly appearance
Bore hole latrine • First introduced by Rockfeller Foundation during 1930 in
campaigns of hook worm control.
• The latrine consists of a circular hole 30 to 40cm in diameter,
dug vertically into the ground to a depth of 4 to 8 m, most
commonly 6m.
• A concrete squatting plate with a central opening and foot rests
is placed over the hole.
• A suitable enclosure is put up to provide privacy
Bore hole latrine 30-40 cm diameter
4 to 8 m depth
Bore hole latrine Merits
• No need for the services of a sweeper for daily removal of night soil.
• Unsuitable for fly breeding
• If located 15 m away from source of water supply, there should be no
danger of water pollution.
Demerits
• Small capacity.
• A special, the auger is required for the construction which may not be
readily available.
• In many places, the subsoil water is high and the soil loose with the result
it may be difficult to dig a hole deeper than 3m.
Dugwell latrine
• A circular pit about 75 cm in diameter and 3 to 3.5
m deep.
• The pits may be lined with pottery rings to prevent
caving in of the soil.
• A concrete squatting plate is placed on the top of
the pit and the latrine is enclosed with a
superstructure.
Dugwell latrine
• 75 cm diameter
3 to 3.5 m deep
Dugwell latrine
Advantages
• It is easy to construct and no special
equipment is needed to dig the hit.
• The pit has a longer life than borehole latrine
because of greater capacity.
Water seal latrine
Two types
• The PRAI type evolved by Planning, Research
and Action Institute, Lucknow
• The RCA type designed by the Research cum
action projects in Environmental sanitation of
the Ministry of Health.
Essential Features of RCA latrine
Location Squatting plate Pan
Trap Connecting pipe Dug well
Superstructure Maintenance
RCA latrine
• Location
15m
Squatting plate
• Made of an impervious material
• It is made of cement concrete
with minimum dimensions of 90
cm square and 5 cm thickness at
the outer edge.
• There is a slope half inch towards
the pan
Pan and Trap
42.5cm
Pan and Trap
• The length 42.5cm. The width of the front portion of the pan has
a minimum of 12.5 cm and the width at its widest portion is
20cm.
• The trap is bent pipe about 7.5cm in diameter and is connected
with the pan.
• It holds water and provides the necessary water seal.
• The water seal is the distance between the level of water in the
trap and the lowest point in the concave upper surface of the
trap.
• The depth of the water seal in the RCA latrine is 2cm.
• Connecting pipe
Connecting pipe 7.5 cm in diameter and at least 1m in length
with a bend at the end.
Dug well
The dug well or pit is usually 75 cm in diameter and 3 to
3.5 m deep and is covered.
• Superstructure
• The desired type of superstructure may be
provided for privacy and shelter.
• Maintenance
• People should be educated to flush the pan after
use with adequate quantity of water.
SEPTIC TANK
Features of a septic tankCapacity The minimum capacity of a septic tank
should be at least 500 gallons
Length The length is usually twice the breadth.
Depth The depth of aseptic tank is from 1.5 to 2m.
Liquid depth
The recommended liquid depth is only 1.2m.
Features of a septic tankAir space A minimum air space of 30cm between the level of
liquid in the tank and the undersurface of the cover.
Bottom The bottom is sloping towards the inlet end.
Inlet and outlet
There is an inlet and outlet which is submerged.
Cover The septic tank is covered by a concrete slab of suitable thickness and provided with a manhole.
Retention period
Septic tanks are designed to allow a retention period of 24 hours.
Septic tanks
Operation and maintenance
• The use of soap water and disinfectants such as phenol
should be avoided.
• Contents of the septic tank should be removed at least
once in a year. This operation is called desludging and it is
disposed by trenching.
• Newly built septic tanks are first filled with water up to the
outlet level and then seeded with ripe sludge drawn from
another septic tank
• It consists of a water
tight chamber filled with
water
• A short length of a
drop pipe from the latrine
floor dips into the water.
4. Aquaprivy
Adv
anta
ges &
Dis
adva
ntag
es • Advantages:
– Cannot be blocked with bulky anal cleaning material
– Nil problem with odor or flies
– Can be connected to a sewerage system at a later date
• Disadvantages:
– Expensive to build
– Need large volumes of water to work
– Water seal may be hard to maintain
– Tanks must be emptied about every 3 years
SULAB SHAUCHALAYA
• The invention of a Patna
based firm
• It consists of specially
designed pan and a water seal
trap.
• It is connected to a pit 3 feet
square and as deep.
LATRINES SUITABLE FOR TEMPORARY USE AND
CAMPS
Shallow trench
latrine
• The trench is 30cm
wide and 90-150cm
deep.
• Its length depend on
the number of
users;3-3.5 m for
100 people.
The trench is 1.8 to 2.5 m deep and 75-90cm wide.
WATER CARRIAGE SYSTEM
Types
Combined sewer system
Separate sewer system.
Elements of water carriage system
• Household sanitary fittings
• House sewers
• Street sewers or trunk sewers
• Sewer appurtenances; manhole, traps etc.
Household sanitary fittings
Two types
• Indian squatting type
• The western commode
type
SEWAGE
SEWAGE
• Sewage is waste water from a community
containing solid and liquid excreta .
• The average amount of sewage which flows
through the sewerage system in 24 hours is
called the dry weather flow.
Health aspects
• Creation of nuisance, unsightliness and pleasant
odours.
• Breeding of flies and mosquitoes
• Pollution of soil and water supplies.
• Contamination of food
• Increased incidence of disease
Composition of sewage
WATER99.9%
SOLIDS0.1%
SEWAGE
Aims of sewage purification
• To stabilize the organic matter so that it can be
disposed off safely.
• To convert the sewage water into an effluent of
an acceptable standard of purity which can be
disposed off into land, rivers or sea.
Strength of sewage
• Biochemical oxygen demand (BOD)
• Chemical oxygen demand(COD)
• Suspended solids
Biochemical oxygen demand (BOD)
• It is defined as the amount of oxygen absorbed by a sample
of sewage during a specified period, generally 5 days at a
specified temperature generally 20 deg C for the aerobic
destruction or use of organic matter by living organisms.
• BOD value range from about 1mg per litre for natural
waters to about 300mg/L for untreated domestic sewage.
• If the BOD is 300mg /L and the above , sewage is said to
be strong, if it is 100mg/L, it is said to be weak.
Chemical oxygen demand(COD)
• The COD test measures the oxygen equivalent
of that portion of the organic matter in a
sample which is susceptible to oxidation by a
strong chemical oxidizer.
Suspended solids
• The amount of suspended solids in domestic
sewage may vary from 100 to 500 ppm.
• If the amount of suspended solids is 100mg/L,
the sewage is said to be weak.
• If the amount is 500mg/L the sewage is said to
be strong.
Decomposition of organic matter
Aerobic process
Anaerobic process
Primary treatme
nt
•Screening •Removal of grit•Plain sedmentation
Secondary
treatment
•Trickling of filters•Activated sludge process
Other method
s
•Sea out fall•River outfall•Sewage farming•Oxidation ponds
Sewered areas
MODERN SEWAGE TREATMENT
Screen Grit Chamber
Final SedimentationTank
Biological Treatment
Primary Sedimentation tank
Sludge Digester
Methane Gas
Sludge drying beds
Primary Treatment Secondary treatment Chlorine
Effluent Disposal Sewage
Primary treat
ment
• Screening
The screen
consists of
vertical or
inclined steel
bars usually set
5cm apart.
Primar
y treatment
Grit chamber
• This chamber is
approximately 10 to 20 m
in length,
• it is so designed as to
maintain a constant velocity
of about 1 foot per second
with a detention period of
30 seconds to 1mt.
Primary treatment
Primary sedimentation
• It is a very large tank
holding from ¼ to 1/3 the
dry weather flow.
• Flow very slowly across the
tank at a velocity of 1 to 2
feet per minute.
• The sewage spends about 6
to 8 hours in the tank.
Secondary treatment
Trickling filter
method
Activated sludge process
The trickling filter
• The trickling filter or
percolating filter is a bed
of crushed stones or
cinker, 1 to 2 m deep and
2 to 30 m in diameter
depending on the size of
the population.
Activated sludge process
• The effluent is mixed with sludge drawn from the final settling
tank.
• The mixture is subjected to aeration chamber for about 6 to 8
hours.
• The aeration is accomplished either by mechanical agitation or
by forcing compressed air continuously from the bottom of the
aeration tank.
• Organic matter of the sewage gets oxidized into carbon
dioxide, nitrates, and water with the help of aerobic bacteria.
Activated sludge process
Secondary sedimentation
• Detained fro 2-3 hours.
• The sludge that collects in the secondary
sedimentation tank is called aerated sludge.
• Part of the activated sludge is pumped back into the
aeration tanks in the activated sludge process and the
rest pumped into the sludge digestion tanks for
treatment and disposal.
Sludge digestion
• Digestion
• Sea disposal
• Land
Digestion
• Incubated under favorable conditions of temperature and pH
• Undergoes anaerobic auto digestion
• Complex solids are broken down into water, carbon dioxide,
methane and ammonia
• The volume of sludge is also considerably reduced.
• Dry readily and form an excellent manure.3-4 weeks or longer
Disposal of effluent
Disposal by dilution
• Diluted in the body of water and impurities are oxidized by
the dissolved oxygen in the water.
• The Royal commission in England (1908) recommended that
an effluent from a sewage treatment plant should not have
more than 30mg/litre of suspended solids and the 5 day BOD
of the effluent including the suspended matter should not
exceed 20mg/litre.
Disposal on land
OTHER METHODS
Sea outfall
River outfall
Land treatment
Oxidation pond
Oxidation ditches
Sea outfall
River outfall
Land treatment (sewage farming)
Oxidation pond
• Open shallow pool 1 to 1.5m depth with an inlet and outlet.
• comprise algae, certain type of bacteria which feed in
decaying organic matter and sunlight
Oxidation ditches
Role of Nurse
• Survey
• Health education
• Construction of disposal units and supervision
• Evaluation
Thank you